Veneer production



Jan. 3, 1967 P. BORK 3,295,571

' VENEER PRODUCTION Filed Feb. 26, 1964 2 sheets-sheet 1 PER oRK A TTORNE YS Jan. 3, 1967 P, BQRK 3,295,571

ER PRODUCT I ON Filed Feb. 26, 1964 -2 Sheets-Sheet 2 INVENTOR. Psa oRK A TTORNE YS lUnited States The present invention vrelates to veneer production by means of a Slicer.

It is the main purpose of the invention to obtain an increased yield in veneer production by means of a Slicer.

It is a further purpose of the invention to provide a composite structure comprising the workpiece which is suitable for veneer slicing with increased yield.

Still a further purpose of the invention is to provide an improved method for veneer production by means of a slicer to obtain increased yield.

Still a further purpose of the invention is to provide an improved veneer slicing method which enables substantially the entire workpiece to be sliced into leaves.

Still a further purpose of the invention is to provide an improved veneer slicing method which reduces idling of the slicer. i

Still a further purpose of the invention is to provide a method of veneer slicing in which an auxiliary member is -used for holding the workpiece firmly in the machine at least during the last partof the slicing operation.

The invention will be further described in the following with reference to the accompanying drawings, in which:

FIG. 1 is a schematic horizontal perspective view of a part of a veneer slicer showing a wooden workpiece according to the invention mounted on its table,

FIG. 2 is Ia corresponding perspective view showing a partly sliced workpiece to illustrate specific advantages of the invention, and

FIG. 3 is a schematic perspective view illustrating the invention in connection with a veneer vertical slicer.

In the drawings only that part of the slicers is shown which is necessary for the understanding of the invention, it being assumed that the general construction of such veneer Slicers is well known to those skilled in the art.

In broad terms, is a workpiece such as a Hitch or square which is adapted to be sliced into leaves by means of a knife 36 which cuts parallel with a surface 12 of the workpiece. On the surface 12 of the work piece which faces the slicer machine table a supporting layer of wood or wood-like material of a thickness which enables the clamping means of the machine to clam-p on its sides only is secured solely by bonding with a bonding force which -at least substantially corresponds to the interior strength of the wood.

The veneer slicer has a supporting table 18 (FiGS. 1 and 2) or 58 (FIG. 3) upon which the workpiece is supported and in operation the slicing is carried on until the bonding zone between the workpiece 1i) and the supporting layer, using the layer only for clamping the workpiece in the machine at least during the last par-t of the slicing operation whereby an increased portion of the workpiece is utilized lfor veneer production in comparison with the conventional methods as will be appa-rent from the toll-owing description.

In FIG. l a slicer table 18 is supported in a frame structure (not shown). Along one longitudinal edge of the table 18, the frame structure has a rigid plate or rail 24 provided with a wooden board 26 on the side which faces the table 18. At the ends of the t-able 18 the length of which may be 12-18 feet the frame structure includes supporting rails (not shown) on which a nlatent rice cutting head generally referred to by 28 is supported 'for rcciprocation. A driving mechanism (not shown) which may comprise flywheels and suitable crank mechanisms reciprocates the -cutting lhead in the direction of'the arrow A. The cutting head -comprises a body portion 30 in which a pressure bar 32 is adjustably supported and which during the reciprocation slides on the top side of the workpiece. The cutting knife 36 is also adjustably supported on the cutting head so as to enable its cutting edge 36 to be adjusted slightly below the undersurface of the pressure bar by a distance which corresponds to the desired thickness of the veneer.

The supporting table 18 is provided with a plurality of slots 26 in each of which a clamping dog 14 is adjustably mounted. Each clamping dog can be vertically adjusted to be clamped against the workpiece at a desired height and by means of power means the clamping dog is brought into clamping engagement with the workpiece, for example by means of hydraulic or pneumatic cylinders (not shown) located under the ta'ble. In many of the commercially available machines of this type an operation panel is provided with individual controls for each of the clamping dogs. When the dogs are clamped the workpiece is clamped into engagement with the wooden board 26.

By means of other hydraulic or pneumatic cylinders (not shown) the supportingV table can be moved vertically and during the slicing operation the table is raised automatically each time the knife movesV back corresponding to the desired thickness of the veneer.

In FIG. l the wooden workpiece is shown in the form of a ditch, eg. a half part of la log of wood. The supporting layer 16 is of such a thickness that the clamping dogs, as illustrated by means of the rear dog 14 of FIG. l is able to clamp the side of the supporting layer only. The supporting layer is of wood or a Iwooddlike material and is secured on the underside of the Hitch solely by bonding.

As will be obvious from FIG. 1 and the -following description it is possible initially t-o clamp the workpiece somewhere between the bottom and the top surface as illustrated by means of the front dog 14 in FIG. l, but when during the slicing operation it becomes necessary the dogs can be moved down and clamped solely on the supporting laye-r 15 during the last part of the slicing operation.

Hereby it is possible to slice the workpiece into veneer leaves completely down to the bonding zone whereby the yield is increased because previously it was necessary to stop the slicing operation before the knife reached the top surface of the dogs. This leaves a board of a thickness of for example V1 inch which could not be utilized.

In the case of a ilitch without any interior defects and being of an expensive wood such as hard tropical wood, this board which is otherwise wasted represents one of the best parts of the ditch, because it is nearest the centre and the grain is usually so regular that it can be cut into veneer leaves which are more valuable.

Previously that wooden board was wasted and could usually only be sold by weight for inferior purposes, particularly because it is usually warped due to the water content of the ilitch which is necessary to condition it for veneer slicing.

Various methods of carrying out the method of the invention will be described in the following examples.

EXAMPLE I A workpiece of tropical wood is conditioned until the water content has been suiciently increased to facilitate the slicing of the veneer. By way of example the iiitch may be submerged in water at 200 F. for a period of 48 hours before the veneer slicing.

3 After the conditioning the broadest surface side of the workpiece is planed, for example in a planing machine. The topside of the workpiece is also planed to a desired surface area parallel with the bottom surface.

It is assumed that prior to the planing the round sides of the itch have been cleaned by removal of bark and impurities, for example by means of cutters.

The workpiece prepared in this way is supported with its broadest side facing upwardly and this side is subjected to infrared rays so as to dry the surface to a depth of for example between 1/32 and inch.

The supporting layer 16 may be prefabricated and be in the form of a layer of plywood having a thickness of for example l inch, a length which corresponds approximately to the length of the workpiece and a width which substantially corresponds to the width of the broadest surface of the workpiece.

In the present example the glue is a contact type glue of neoprene type, i.e. a glue which contains a synthetic rubber in a suitable solvent or a mixture of synthetic and/or natural rubber in a solvent. Such glue is a commercially available item which can be supplied by a gluemanufacturer according to the customers specification, i.e. information about the types of material to be bonded and a stipulation that the glue must have a strength which is substantially equal to or higher than the interior strength of the wood. Specific examples of neoprene glues are P. B. Flitch Glue supplied by F. Heimann & Co. of Denmark and clean neoprene cont-act glue sold under the tradename Casco by Leicester, Lovell & Co. of England.

The glue is irst applied to the surface of the supporting layer 16 which is cold. The glue may be applied to the surface in any convenient manner, for example by spraying, by brushes, by pouring out and scraping or in any other convenient manner, until a suitable layer is obtained. Preferably the glue is applied to the surface of the supporting layer 12 during the surface drying of the workpiece and thereafter to the surface-dried workpiece which is still warm so that the glue will be dried to substantially the same extent on the two surfaces at nearly the same time due to the quicker drying of the glue on the warm surface.

After a few minutes, the precise time depending on the nature of the glue and of the surfaces of the workpiece and the supporting layer respectively the two surfaces are brought into contact and are pressed togetherwith a pressure which may be of the order of -15 k. per cm?, but again which depends on the nature of the glue. A glue manufacturer familiar with the production of glue in the wood working industry will easily be able to specify the optimum pressure for the type of wood and the type of glue in each individual case, as well as the time necessary to enable the glue to set to the desired bonding strength which as hereinbefore mentioned must be substantially equal to or slightly more than the interior strength of the wood.

The combined workpiece and layerY is supported on the -machine t-able 18 and clamped in the manner hereinbefore described. The clamping dogs are for example in the first instance adjusted to clamp half way up the workpiece. The machine table is raised until the planed top surface of the workpiece is substantially at the horizontal level of the knife, so that when the machine is started the knife will be able to cut a clear veneer leaf after only a few reciprocations. The slicing is continued until the knife is near the clamping dogs. The machine is then stopped and the clamping dogs moved down so as to clamp on the supporting layer 16 only. The machine is restarted and the slicing continued until the bonding zone is reached.

By carrying out the slicing according to the method herein described an increased yield of up to 8-10% can be obtained compared with what is normally the case when a board of the workpiece is left as waste.

4 By planing the top surface of the workpiece preferably in conjunction with the planing of the undersurf-ace an increased capacity of the machine is also obtained, be-l cause the workpiece can initially be raised to a horizontal level which is very close to that of the knife. Otherwise it is usual to let the knife cut the top surface to planed state whereby waste of machine time occurs. In this way the effective machine time may be increased by up to about 6%.

EXAMPLE II The method is carried out as described in Example I with the difference that the surface drying of the planed surface of the itch is carried out by high frequency treatment for example by means of a tul-a which is designed to dry the surface to a depth between 1%2 and /g inch.

Such high frequency treatment is well-known in the artV and high frequency equipment as well as a tula can easily be designed for this purpose by those skilled in the art.

EXAMPLE VIII The method is carried out as described in Example I with the difference that instead of surface drying the surface of the itch by means of infrared rays a chemicall treatment is used.

For this purpose a volatile substance or a mixture thereof can be used.

For example a mixture of methylalcohol and acetone in a proportion of 1:1 or a mixture of ethylalcohol and acetone in a proportion of 1:1 may be used. v

Other chemical substances or mixtures thereof for carrying out the surface drying in this manner will be readily apparent to those skilled in the art.

EXAMPLE IV EXAMPLE V The method is carried ont using surface drying accord-` ing to any of Examples I-IV.

Instead of using a neoprene type contact glue a casein glue is used which is so formulated that the glue can harden to provide the necessary strength while the surface layer is still dry.

When a casein glue is used it will be necessary to press the two pieces together for somewhat longer time which may be about 15 minutes time specied by the glue manufacturer.

EXAMPLE VI The broad surface of a workpiece is planed before the water or steam treatment and the planed surface is surface dried in any of the manners described in Examples I-IV. The supporting layer is bonded to the planed surface 4before the conditioning.

In such a case .a glue must be used which is resistant to water and heat, but again a suitable type can readily be supplied by those skilled in the adhesive art.

As an example a neoprene type glue to which a suitable hardening agent has been added may be used.

An epoxy type or a polyester type glue with a suitable hardening agent added may also be used.

Depending on the type of glue selected it may be necessary to keep the workpiece and the supporting layer pressed together for some time before the conditioning treatment, or to decrease the setting time of 4the glue by suitable treatment such as high frequency treatment.

The workpiece with the supporting layer bonded to it is thereafter subjected to conditioning as described in Example I. Y

After the conditioning the `top surface of the workpiece is planed, it is clamped in the machine and the slicing is performed as described in Example I.

EXAMPLE VII In the preceding examples the slicing of warm workpieces which have been conditioned has been described.

Certain types of wood for example maple and beech can, however, be sliced cold making use of their natural water content to facilitate slicing without there being need for conditioning treatment. In such cases the method can be carried out in the following manner:

The cold flitch is planed on opposite surfaces as described in Example I, whereafter the planed bottom surface is surface. dried in any of the manners described in Examples I-IV.

The supporting .layer is thereafter glued on to the planed and surface dried bottom surface of the workpiece using a cold hardening glue of a type which also can easily be selected bythose skilled in the art from types available as commercial products.

A neoprene type contact glue Aas described in'Example I or a casein glue as described in ExampleV V may be used.

Urea-formaldehyde glues or resinoustypeglues with a hardening agent mayalso'ibe used.

When the glue has. hardenedr the cold workpiece is clamped inthe machine'V ands'licedV as described in Example I.

Instead of using yplywoodas. the supportinglayer it is possible to use a supportinglayerin'the form of a plurality of boards. In view of the fact that 'durin'gthe last part of the slicing operation the clamping dogs engage the edge of the supporting layer the boards shouldpreferably be bonded together initongued and grooved relation'- ship.

Instead of usual wood assuppo'rting layer it is also possible to use wood-like' substances such as artificial woodor chip board.

In a veneer factory which contemplates adopting the invention it will be possible instead of selling the waste boards to store them and use them for supporting layers. It will also be appreciated that in so far as the slicing is only continued down to the bonding zone the same supporting layer may be used many times over, if necessary after planing of the surface.

The use of plywood or similar strong supporting layer which is resistant to warping has the advantage that it will be able'to keep the underside of the workpiece flat, even in the event that internal forces occur during the slicing which otherwise would Vcause the workpiece to warp. Such warping could result yin veneer leaves of uneven thickness. Obviously with this invention this risk is minimal and Vthereby an Vincreased yield of veneer is obtainable.

In many cases logs of tropical wood have interior cavities of irregular configuration. Usually such cavities are visible at the end of the log and in such event the longitudinal cut to form the workpiece or flitch will be chosen in such a way that the largest extension of the interior cavity will lie substantially along the cutting surface. It is, however, not possible to see from the ends of the log exactly how the cavities are in the interior of the log and it will often be found that a workpiece cut from such a log can only `be used for veneer slicing for a part of its depth, because when the knife cuts through the interior cavity the workpiece will be split into two parts and therefore is no longer effectively clamped on the table.

Cutting of such workpieces, therefore, requires special care and must be done slowly, because if the slicing is continued until the workpiece splits the clamping dogs may damage the knife. In any event such careful cutting does not utilize the machine time to best advantage and reduces, in addition to the waste, the economy of the veneer production.

The method of the invention also facilitates the slicing of itches of the type which are usually referred to as itches with a bad heart.

FIG. 2 illustrates the slicing of such a workpiece or a iiitch according to the method of this invention.

In FIG. 2 the flitch is shown partly sliced with the part sliced away indicated in dotted lines.

The bad heart itch has a cavity 11 of irregular configuration which includes an upwardly extending cavity portion 13.

Were the supporting layer 16 bonded to the underside of the flitch it would during conventional production be necessary to stop the slicing before the upwardly extending cavity portion was reached so as to prevent the itch from breaking in a longitudinal direction under the inuence of the clamping force.

However, by having the flitch bonded on the supporting layer 16 the only thing which happens during the slicing operation is that during the last part of the slicing operation as illustrated in FIG. 2 each cut produces two veneer sheets 40 and 42 because the support layer 16 keeps the two half parts of the liitch secured on each side of the bad heart so that the slicing can be carried on down to the bonding zone as hereinbefore described.

It Will be appreciated that with ilitches of this type depending on the extension and configuration of the interior cavity it is possible to obtain a substantially increased yield by usingthe present invention.

In the schematically shown embodiment of the machine of FIGS. l and 2 the fiitch is stationary during the slicing operation-apart from the distance which it is raised during each reciprocation of the cutting knife.

In the machine schematically shown in FIG. 3 the machinefis provided 'with a substantially vertical table 58 whichy is reciprocated in a vertical plane in the direction of the arrow B in parallel relationship with a cutting knife 54 which is stationary. In the embodiment of FIG. 3 the machine table 58 is provided with slots 50 and 52 in which clamping dogs 64 are movable from both sides to clamp the workpiece, only the upper clamping dogs being visible in FIG. 3.

Also in FIG. 3 a workpiece with a supporting layer 16 bonded on the side thereof is shown.

Obviously with the vertical arrangement of the workpiece in FIG. 3 the bonding zone is subjected to a greater shear than in FIGS. 1 and 2 and it will therefore be advisable to clamp on the workpiece itself until the slicing has been carried through close to what usually will be the waste and then thereafter clamp on the supporting layer 16.

It is also advisable that the bonding strength of the glue is somewhat higher than the interior strength of the wood.

It will readily be appreciated that both the application of the glue and the subsequent mounting of the composite structure in the slicer must be performed without undue delay. The early application of the glue which should have a relatively short setting time is necessary as any substantial delay will result in the previously dried surface of the workpiece again becoming moist. The early mounting of the workpiece is necessary because slicing must take place before the workpiece has cooled down to such an extent that it is no longer adequately conditioned.

It is to be understood that the invention is not limited to the examples shown and described with reference to the drawings.

It is possible instead of using wood as a supporting layer to use any other suitable material such as a plastic material having equivalent properties to wood and which will not damage the cutting knife, even if it cuts through the bonding zone. Y

The invention may also be applied to the production of artificial veneers by slicing a workpiece which is produced by bonding a stack of veneer sheets together in the form of a sandwich with the grains of the individual veneer sheets extending in substantially the same direction, conditioning the sandwich for slicing and then slicing the sandwich transversely to the glue lines.

When using the present invention in connection with such production the sandwich block is cut at one longitudinal edge transversely to the glue zones, the supporting layer is bonded to the surface planed whereafter the block is mounted in the slicer and the slicing carried out as hereinbefore described.

Obviously a sandwich block for such veneer production is an expensive item and the saving afforded by the present invention is substantial.

It is also t be understood that also other ways of surface drying the workpiece may be used. For example certain kinds of wood which can withstand such treatment or wood which it is desired to stain can be treated with ammonia, in which case, of course, means for exhausting the vapours must be provided.

I claim: 1. A method of producing veneer leaves 'by slicing a wooden workpiece substantially parallel with` a surface thereof during firm clamping of said workpiece, comprising the steps of surface drying said surface of said workpiece,

providing a composite structure comprising said workpiece and a layer of a material that will not damage the knife of the veneer slicing machine, having a thickness enabling the clamping to be effected on the sides of said layer only, by bonding said layer on said workpiece surface by means of a bonding agent capable of setting to effectively provide a bonding strength at least substantially corresponding to the interior strength of said wooden workpiece,

clamping said composite structure firmly and slicing veneer leaves of the workpiece of said composite structure until the bonding zone between said workpiece and said layer is reached during clamping only on the sides of said layer during the last part of the slicing operation.

2. Using the layer of a material that will not damage the knife of the veneer slicing machine repeatedly in carrying out the method as claimed in claim 1 with subsequent workpieces.

3. Performing the surface drying of the workpiece by infrared rays in the method as claimed in claim 1.

4. Performing the surface drying of the workpiece by high frequency heating in the method as claimed in claim 1.

5. Performing the surface drying of the workpiece by hot air in the method as claimed in claim 1.

6. A method of producing veneer leaves by slicing a wooden workpiece substantially parallel with a surface thereof during firm clamping of said workpiece, comprising the steps of surface drying said surface of said workpiece by means of volatile chemical substances,

providing a composite structure comprising said workpiece and a layer of a material that will not damage the knife of the veneer slicing machine, having a thickness enabling the clamping to be effected on the sides of said layer only, by bonding said layer on said workpiece surface by means of a bonding agent capable of setting to effectively provide a bonding strength at least substantially corresponding to the interior strength of said workpiece,

clamping said composite structure and slicing veneer leaves of the workpiece of said composite structure until the bonding zone between said workpiece and said layer is reached during clamping only on the sides of said layer during the last part of the slicing operation.

7. Performing the surface drying of the method as claimed in claim 6 by means of a mixture of a volatile fluid which is miscible with water and a more volatile fiuid which is not miscible with water.

8. Using a mixture of alcohol and acetone in the method of claim 7.

9. A method of producing veneer leaves by slicing a wooden workpiece which is held firmly clamped substantially parallel with a surface parallel with which theslicing is effected,

comprising the steps of preparing said workpiece for slicing by elevating its temperature, drying a surface layer of said surface of said workpiece, bonding on said dried surface of said workpiece a layer of a material that will not damage the knife of the veneer slicing machine having a thickness which enables the clamping to be effected .on said layer only by means-of a bonding agent capable of setting to effectively provide a bondingl strength at least substantially corresponding to the interior strength of said wooden workpiece to effectively provide a unitary structure comprising said workpiece and said layer, clamping said structure to hold it firmly for slicing and thereafter, slicing veneer leaves of .the workpiece of said structure until the bonding zone between" said workpieceand saidlayer is reached during clamping only on said layer during the last part of the slicing operation. 10. Carrying out the method of claim 9 by applying a neoprene contact glue on the surfaces to be bonded together, allowing the glue to dry up to binding condition and thereafter pressing the parts together.

11. Applying the glue on the surface of the layer while the surface drying of the workpiece is effected in the method of claim 10.

12. A method of producing veneer leaves by slicing a wooden workpiece ona slicing machine having a support including clamping means operable to clamp the workpiece with an unexposed surface thereof facing said support, a cutting knife, means for adjusting the initial mu tual level between the machine support and the knife and means for providing mutual reciprocation between said knife and said workpiece so as to slice from an exposed surface of said workpiece opposite the surface which faces the support, comprising the steps of planing the exposed surface into substantially parallel relationship with the surface which is adapted to face the machine support, surface-drying said unexposed surface of said workpiece, providing a composite structure comprising said workpiece and a layer of a material that will not damage the knife of the veneer slicing machine, having a thickness enabling said machine clamping means to clamp on the sides of said layer only, by bonding said layer on said Iunexposed workpiece surface lby means of a bonding agent capable of setting to effectively provide a bonding strength at least substantially corresponding to the interior strength of said wooden workpiece,

supporting said composite structure on said slicing machine support with said layer engaging said machine support, clamping said composite structure bysaid clamping means, adjusting the machine to start slicing substantially at` the level of the planed exposed surface of the workpiece, and

slicing veneer leaves of the workpiece of said composite structure until the bonding zone between said workpiece and said layer is reached during clamping only on the sides of said layer during the last part of the slicing operation. l,

13. A method of producing veneer leaves by slicing a wooden workpiece substantially parallel with a surface thereof while holding the workpiece firmly clamped,

comprising the steps of preparing said workpiece for slicing by elevating its temperature,

drying a surface layer of said surface of saidworkpiece,

bonding a layer of a material that will not damage the knife of the veneer slicing machine having a thickness which enables the clamping to be effected on said layer on said dried surface of said workpiece substantially immediately after the drying by means of a bonding agent capable of setting to effectively provide a bonding strength at least substantially corresponding to the interior strength of said wooden workpiece to effectively provide a unitary structure comprising said workpiece and said layer, clamping said structure to hold it firmly for slicing and thereafter, Y slicing veneer leaves of the workpiece of said structure until the bonding zone between said workpiece and said layer is reached duringY clamping only on said layer during the last part of the slicing operation. 14. A method of producing veneer leaves by slicing a wooden workpiece substantially parallel with a surface thereof while holding the workpiece firmly clamped, drying a surface layer of said surface of said workpiece,

bonding a layer of a material that will not damage the knife of the veneer slicing machine having a thickness which enables the clamping to be effected on said layer on said dried surface of said workpiece, only by means of a bonding agent which is resistant to heat and moisture and is capable of setting to effectvely provide a bonding strength at least substantially corresponding to the interior strength of said wooden workpiece to effectively provide a unitary structure comprising said workpiece and said layer, conditioning said structure for slicing by elevating its temperature, clamping said structure to hold it firmly for slicing and slicing veneer leaves of the workpiece of said structure until the bonding zone between said workpiece and said layer is reached during clamping only on said layer during the last part of the slicing operation. 15. A method of producing veneer leaves by cold slicing a wooden workpiece substantially parallel with a surface thereof while holding the workpiece firmly clamped,

drying a surface layer of said surface of said workpiece, bonding a layer of a material that will not damage the knife of the veneer slicing machine having a thickness which enables the clamping to be effected on said layer on said dried surface of said workpiece, only by means of a cold setting bonding agent capable of setting to effectively provide a bonding strength at least substantially corresponding to the interior strength of said wooden workpiece to effectively provide a unitary structure comprising said workpiece and said layer, clamping said structure to hold it firmly for slicing, and cold slicing veneerV leaves of the workpiece of said structure until the bonding zone between said workpiece and said layer is reached during clamping only on said layer during the last part of the operation. 16. A method of making parallel planar cuts to produce veneer from substantially the whole of Wooden blocks, clamped at the bench of a veneer slicing machine, comprising the steps of:

rigidly bonding, to the surface of the block to face the bench, a support that consists of a substance that will not damage the knife of the veneer slicing machine and that has such a thickness that the clamping means of the veneer slicing -machine can engage the lateral edges of the support for clamping the block thereon at the machine; during the last stage of the slicing operation, engaging the clamping means solely at the lateral edges of the support so that they will not interfere with the slicing of the block closely adjacent to the support; and slicing substantially the entire b-lock parallel to the bon-ded surface of the support until the support is reached by the knife of the slicing machine.

17. The method according to claim 16, wherein the support is rigidly bonded by drying the bottom side of the block t-o be sliced and using a bonding agent to bond the support to the block.

18. The method of claim 16, wherein the bonding is the sole means employed to rigidly hold the block and support together and the bonding agent has a strength at least equal to the resistance offered by the wood of the block against the knives.

19. The method `of claim 16, including the preliminary step of providing a veneer slicing machine having a flat planar work bench, slicin-g Imeans for reciprocatin-g parallel to the bench, means for adjusting the initial mutual level between the machine bench and the knife, and clamps for clamping a workpiece wooden block onto the bench.

20. The method of claim 16, including the preliminary step before bonding :of soaking the wooden -block in water until it is substantially saturated, cutting a at planar surface on the wooden block to face the bench, and planing a flat surface on the opposite side of the wooden block that is substantially parallel to the surface of the block t-o face the bench.

UNITED STATES PATENTS 1,394,119 10/1921 Rockwell 161-38 1,997,996 4/ 1935 Carstens 161-38 2,562,976 8/1951 Winnick 161-38 2,770,272 11/ 195 6 Morrison 144-317 FOREIGN PATENTS 10/ 1949 Great Britain.

WILLIAM W. DYER, JR., Primary Examiner. B, I, Assistent E Jaminr, 

6. A METHOD OF PRODUCING VENEER LEAVES BY SLICING A WOODEN WORKPIECE SUBSTANTIALLY PARALLEL WITH A SURFACE THEREOF DURING FIRM CLAMPING OF SAID WORKPIECE, COMPRISING THE STEPS OF SURFACE DRYING SAID SURFACE OF SAID WORKPIECE BY MEANS OF VOLATILE CHEMICAL SUBSTANCES, PROVIDING A COMPOSITE STRUCTURE COMPRISING SAID WORKPIECE AND A LAYER OF A MATERIAL THAT WILL NOT DAMAGE THE KNIFE OF THE VENEER SLICING MACHINE, HAVING A THICKNESS ENABLING THE CLAMPING TO BE EFFECTED ON THE SIDES OF SAID LAYER ONLY, BY BONDING SAID LAYER ON SAID WORKPIECE SURFACE BY MEANS OF A BONDING AGENT CAPABLE OF SETTING TO EFFECTIVELY PROVIDE A BONDING STRENGTH AT LEAST SUBSTANTIALLY CORRESPONDING TO THE INTERIOR STRENGTH OF SAID WORKPIECE, CLAMPING SAID COMPOSITE STRUCTURE AND SLICING VENEER LEAVES OF THE WORKPIECE OF SAID COMPOSITE STRUCTURE UNTIL THE BONDING ZONE BETWEEN SAID WORKPIECE AND SAID LAYER IS REACHED DURING CLAMPING ONLY ON THE SIDES OF SAID LAYER DURING THE LAST PART OF THE SLICING OPERATION. 